#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mxN = (int)3e3+10;
const int MOD = (int)1e9+7;
int n, m, dp[mxN][mxN];
int32_t main() {
cin >> n >> m;
for(int i = 0; i < mxN; i++) dp[i][0]=dp[0][i]=1;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
dp[i][j] += dp[i-1][j]; // empty row
dp[i][j] += 4*j*dp[i-1][j-1]; // exactly 1 on row
if(j>1) dp[i][j] += (j-1)*j/2*dp[i-1][j-2]; // exactly 2 on row
if(i>1) dp[i][j] += j*(i-1) * dp[i-2][j-1]; //1 on both row and col
dp[i][j]%=MOD;
}
}
cout << (dp[n][m]+MOD-1)%MOD << "\n";
}
